When asked which of the two types of enthusiasm he regarded as the more beneficial, Andrew Carnegie replied: “That depends upon the circumstances. Passive enthusiasm always precedes the expression of active enthusiasm, as one must feel enthusiasm before he can express it in any form.

“And there are times when the active expression of enthusiasmmay be detrimental to one’s interests, as it may indicate over-eagerness or anxiety, or disclose one’s state of mind when he does not wish it to be known to other.
“It is highly important that one learns to withhold the expression of his feelings whenever he wills to do so. It is also important to learn to turn on enthusiasm and give it any desired form of expression at will. In both instances the control is the important factor.
Enthusiasm inspires personal initiative, both in thought and physical action. It is very difficult for one to do his best in any kind of endeavor for which he does not feel and display enthusiasm.
“It dispels physical fatigue and overcomes laziness. It stimulates the nervous system and causes it to perform its duties more effectively, including particularly the digestion of food. For this reason the meal hour should be the most pleasant hour of the day. It should never be made the occasion for settling personal or family differences of opinion; nor should it become the time for the correction of the faults of children.
“Positive enthusiasm discourages all forms of negative thought, and dispels fear and worry. Thus it prepares the mind for the expression of faith, which is the most powerful of all forms ofenthusiasm. It is important that one learn the difference between negative and positive enthusiasm, since enthusiasm is the starter which puts the subconscious mind to work.
“Enthusiasm is the twin brother of the will, and is the major source of persistent, sustained action of the will. Will power, persistence and enthusiasm are triplets which give one sustained action with a minimum loss of physical energy.
“Emerson spoke no greater truth than when he said: Nothing great was ever achieved without enthusiasm.”
Source: PMA Science of Success. Educational Edition. The Napoleon Hill Foundation. 1961. Pgs. 250-251.